Generally, a wireless local area network system includes an access point and a station (STA). Wireless data transmission may be performed between the access point and the station, so as to form a wireless network. The access point is equivalent to a bridge connecting a wired network and a wireless network. The access point connects various stations together, and then connects the wireless network to an Ethernet, so as to implement communication between the stations and the wired network.
In the prior art, data between the access point and the station is transmitted via a wireless medium, and access to the wireless medium is generally controlled through a coordination function, which includes two types: a distributed coordination function (DCF) and a point coordination function (PCF). The point coordination function is a noncompetitive mechanism, that is, an access point polls stations, so as to control access of the stations; therefore, a collision does not occur between stations under the PCF mechanism. However, currently there are few products supporting the PCF mechanism, so that a WLAN can hardly support the PCF mechanism. For most transmission operations in the WLAN, a distributed coordination function mechanism is adopted.
The DCF is a competitive mechanism. Before attempting to send data to an access point, a station detects whether the access point is in an idle state. If the access point is in the idle state, the station sends the data to the access point. If the access point is in a busy state, the station needs to delay its access, and uses an exponential backoff algorithm to randomly allocate a random backoff time value within the range of a contention window. When the delay reaches the backoff time value, the station competes again to access the access point. However, the inventor of this application finds out in long term researches that, because the waiting time of each station is a randomly allocated value, the station may collide again with other stations when accessing the access point again. The value of collision recurrence is related to the number of stations waiting for access. Generally, the more the stations wait for access, the more easily the collision occurs again. Therefore, when too many users concurrently access an access point in a WLAN, a significant access collision may exist, which may lead to a tremendous drop of uplink throughput of the WLAN.